<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    #d1{
      width: 100px;
      height: 100px;
      border: 10px solid red;
        /*圆角 值越大越圆,超过宽高一半时为正圆(前提是正方形)*/
        border-radius: 100px;
    }
    #d2{
        width: 50px;
        height: 100px;
        border: 1px dashed red;
        /*内边距会影响元素的宽高*/
        padding-left:50px ;
    }
  </style>
</head>
<body>
<div id="d2">内边距</div>
<div id="d1"></div>
</body>
</html>